The use of water from coal seam gas for growing pasture has received a cautious response from a Newcastle University Professor.

Professor Garry Willgoose says the use of so called 'produced water' from the wells does prompt concerns.

The gas company AGL has been talking up the benefits of a trial using water from coal seam gas wells on crops in Gloucester.

Since April, the company has been using both standard irrigation and 'produced water' on two types of crops to grow livestock feed.

Mike Moraza, spokesperson for the company denies it's a public relations exercise suggesting it's an example of how AGL can innovate and create solutions to reuse the slightly saline water produced as part of the production process.

He says the company has been growing forage triticale and lucerne on a property near Gloucester with success suggesting the silage was 'highly sought after'.

"More than 65 tonnes of triticale silage bales has been harvested since the trial began and sold to local farmers desperate to feed their livestock during a recent dry spell. In short, the crops are thriving," he said.

But Professor Garry Willgoose from the University of Newcastle agrees the "produced water" can be used, but believes the practice needs to be closely monitored.

He says irrigators need to make sure more water than the plant technically requires is used.

"So the saline water is flushed through the root zone," said Professor Willgoose.

"And the more saline the water, the more water you have to put on, in excess of the technical demand of the plant.

"If you don't put enough water on the salt will built up in the soil creating a major problem in years to come."